Rho Persei

ρ Persei
Location of ρ Persei (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Perseus
Right ascension 03h 05m 10.59385s[1]
Declination +38° 50′ 24.9943″[1]
Apparent magnitude (V) +3.39[2]
Characteristics
Evolutionary stage AGB[3]
Spectral type M4 II[4]
U−B color index +1.79[2]
B−V color index +1.65[2]
Variable type SRb[4]
Astrometry
Radial velocity (Rv)+29.10±0.30[5] km/s
Proper motion (μ) RA: +129.22[1] mas/yr
Dec.: –105.70[1] mas/yr
Parallax (π)10.60 ± 0.25 mas[1]
Distance308 ± 7 ly
(94 ± 2 pc)
Absolute magnitude (MV)−1.7[6]
Details[7]
Mass1.9±0.7 M☉
Radius143±12 R☉
Luminosity2,692+192
−180 L☉
Surface gravity (log g)0.37±0.15 cgs
Temperature3,479±125 K
Metallicity [Fe/H]−0.15 dex
Rotational velocity (v sin i)11.2[8] km/s
Age440[9] Myr
Other designations
Gorgonea Tertia, Rho Per, ρ Per, 25 Persei, BD+38°630, FK5 109, GC 3682, HD 19058, HIP 14354, HR 921, SAO 56138, PPM 68074[10]
Database references
SIMBADdata

Rho Persei, Latinized from ρ Persei, is a star in the northern constellation of Perseus. It has the traditional name Gorgonea Tertia /ɡɔːrɡəˈniːə ˈtɜːrʃə/,[11] being the third member of the quartet called the Gorgonea in reference to the Gorgons from the legend of Perseus.[9] An apparent visual magnitude of +3.39[2] makes it visible to the naked eye, but a challenge to view from a well-lit urban environment. Based upon parallax measurements, it is located at a distance of roughly 308 light-years (94 pc) from Earth.[1]

A visual band light curve for Rho Persei, plotted from AAVSO data[12]

Rho Persei is a semiregular variable star, whose apparent magnitude varies between 3.3 and 4.0[13] with periods of 50, 120 and 250 days.[6] The star has reached the asymptotic giant branch of its evolution.[3] It is a bright giant star with a stellar classification of M4 II.[4] The outer envelope has an effective temperature of 3,479 K,[7] giving it the red-orange hue of an M-type star.[14]

This star has a mass 1.9 times the mass of the Sun, while its radius has expanded to 143 times solar. It is radiating some 2,700 times the Sun's luminosity.[7] Rho Persei is losing mass at the rate of 1.2×10−8 solar masses per year, or the equivalent of the Sun's mass every 83 million years.[15] It is about 440 million years in age.[9]

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